Image-Based High-Content Analysis, Stem Cells and Nanomedicines: A Novel Strategy for Drug Discovery - Harnessing Biomaterials in Nanomedicine: Preparation, Toxicity, and Applications - page 268

of an embryo [26], while the slightly more specialized multipotent
cells that reside in the tissues and organs of multi-cellular organisms
are much more restricted in their “choice” of cellular fate. Recently,
it has been shown that some adult stem cells, under certain culture
conditions, are able to diff erentiate into other cell types unusual to
their tissue of origin [27].

9.3.2 Human Embryonic Stem Cells

Exploiting the great potential that lies in human ESC (hESC) would be
an immense advantage in our attempt to improve the drug discovery
process.
The ESC research started with seminal studies in murine embryos
obtained by in vitro fertilization in the 1970s and 1980s [26, 28]. This
conduced to the current ability to generate and maintain human ESC
in culture by the late 1990s [29]. Since hESCs are the progenitors
of all the cells in the human body, we can deduce that they have the
capability, under the correct conditions, to be “guided” to form the
cells needed for any potential drug screening.
This unlimited potential is in fact both a blessing and a curse for our
purposes. Clearly it is a blessing in the sense that ESCs can eventually
be used to diff erentiate into virtually any cell type that, in turn, can
be employed as a screening tool for almost any disease. As a result of
their pluripotency, however, it is also an immensely complex task to
direct such cells homogenously to a specific desired fate [30]. Difficult
as this may be, in recent years great leaps have, nonetheless, been
made in this area and more and more protocols are being developed
[31-34]. Other problems that arise when considering wide-scale use
of hESCs are the ethical concerns of some financing and federal bodies
in funding research using these types of cells [35]. However, the way
in which hESC are currently being obtained is slowly producing a gain
in the number of supporters, or at least is allowing the possibility
to obtain these cells from in vitro fertilized embryos with serious
genetic diseases, since it is based on the use of embryos discarded
following pre-implantation genetic diagnosis (PGD) procedures.
In such procedures, the embryos selected for research (at the early
blastocyst stage) were found positive for a genetic disorder and would
never be implanted into the mother's uterus [36, 37]. These off er
good platform tools by which to study basic cellular and molecular
mechanisms of inheritable diseases such as Huntington's disease [38],